1. Field of the Invention
The present invention relates to vehicle navigation and flow management. More particularly, this invention relates to methods and systems for airlines or aviation/airport authorities to better manage the flow of a plurality of aircraft into and out of a system or set of system resources.
2. Description of the Related Art
The need for and advantages of management operation systems that optimize complex, multi-faceted processes have long been recognized. Thus, many complex methods and optimization systems have been developed. However, as applied to management of the aviation industry, such methods often have been fragmentary or overly restrictive and have not addressed the overall optimization of key aspects of an aviation authority's regulatory function, such as the flow of a plurality of arrival/departure aircraft to/from a system resource or set of system resources.
The patent literature for the aviation industry's operating systems and methods includes: U.S. Pat. No. 6,463,383, issued Oct. 8, 2002 to the present applicants and entitled “Method And System For Aircraft Flow Management By Aviation Authorities;” U.S. Pat. No. 5,200,901, issued Apr. 6, 1993 to Gerstenfeld and entitled “Direct Entry Air Traffic Control System for Accident Analysis and Training;” U.S. Pat. No. 4,196,474, issued Apr. 1, 1980 to Buchanan & Kiley and entitled “Information Display Method and Apparatus for Air Traffic Control;” United Kingdom Patent No. 2,327,517A—“Runway Reservation System,” and PCT International Publication No. WO 00/62234—“Air Traffic Management System.”
Aviation regulatory authorities (e.g., various Civil Aviation Authorities (CAA) throughout the world, including the Federal Aviation Administration (FAA) within the U.S.) are responsible for matters such as the separation of in-flight aircraft. In an attempt to optimize their regulation of this activity, most CAAs have chosen to segment this activity into various phases (e.g., taxi separation, takeoff runway assignment, enroute separation, oceanic separation, arrival/departure sequencing and arrival/departure runway assignment) which are often sought to be independently optimized.
These optimizations are usually attempted by various, independent ATC controllers. Unfortunately, this situation often appears to result in optimization actions by individual parts of the airspace system (e.g., individual controllers or pilots) which have the effect of reducing the aviation industry's overall safety and efficiency.
There appears to have been few successfull attempts by the various airlines/CAAs/airports to make real-time, trade-offs between their different segments and the competing goals of these segments as it relates to optimizing the safe and efficient movement and flow of aircraft. For example, in the sequencing of the arrival/departure flow of aircraft to an airport, it often happens that some sequencing actions are taken too early (e.g., ground holds on aircraft before enough data is available to determine the validity of an apparent constraint in the arrival flow at the destination airport; see PCT International Publication No. WO 00/62234—“Air Traffic Management System”) or too late (e.g., when an aircraft is within 50 to 100 miles from an airport) to resolve a problem.
To better understand these aviation processes, FIG. 1 has been provided to indicate the various segments in a typical aircraft flight process. It begins with the filing of a flight plan by the airline/pilot with a CAA. Next the pilot arrives at the airport, starts the engine, taxis, takes off, flies the flight plan (i.e., route of flight), lands and taxis to parking. At each stage during the movement of the aircraft on an IFR flight plan, the CAA's Air Traffic Control (ATC) system must approve any change to the trajectory of the aircraft. Further, anytime an aircraft on an IFR flight plan is moving, an ATC controller is responsible for ensuring that an adequate separation from other IFR aircraft is maintained. During the last part of a flight, initial arrival sequencing (accomplished on a first come, first serve basis, e.g., the aircraft closest to the arrival fix is first, next closest is second and so on) is accomplished by the enroute ATC center near the arrival/departure airport (within approximately 100 miles of the airport), refined by the arrival/departure ATC facility (within approximately 25 miles of the arrival airport), and then approved for landing by the arrival ATC tower (within approximately 5 miles of the arrival airport).
For example, current CAA practices for managing arrivals at destination airports involve sequencing aircraft arrivals by linearizing an airport's traffic flow according to very structured, three-dimensional, aircraft arrival paths, 100 to 200 miles from the airport or by holding incoming aircraft at their departure airports. For a large hub airport (e.g., Chicago, Dallas, Atlanta), these paths involve specific geographic points that are separated by approximately ninety degrees; see FIG. 2. Further, if the traffic into an arrival fix for an airport is relatively continuous over a period of time, the linearization of the aircraft flow is effectively completed hundreds of miles from the arrival fix. This can significantly restrict all the aircraft's arrival speeds, since all in the line of arriving aircraft are limited to that of the slowest aircraft in the line ahead.
Unfortunately, if nature adds a twenty-mile line of thunderstorms over one of the structured arrival fixes—the flow of traffic stops. Can the aircraft easily fly around the weather? Many times—yes. Will the structure in the current ATC system allow it? No. To fly around the weather, an arriving aircraft could potentially conflict with the departing aircraft which the system dictates must climb out from the airport between the arrival fixes.
The temporal variations in the flow of aircraft into an airport can be quite significant. FIG. 3 shows for the Dallas-Ft. Worth Airport the times of arrival at the airport's runways for the aircraft arriving during the thirty minute time period from 22:01 to 22:30. It can be seen that the numbers of aircraft arriving during the consecutive, five-minute intervals during this period were 12, 13, 6, 8, 6 and 5, respectively. While some of these variations are due to the aircraft's planned scheduling differences, much of it is also seen to be due to the many decisions, independent in nature, that impact whether a scheduled flight will arrive at its fix point at its scheduled time. These decisions may include whether a customer service agent shuts a departing aircraft's door at the scheduled time or maybe waits for some late, connecting passengers, or the personal preferences that the pilots exhibit in setting their flight speeds for the various legs of their flights. These types of independent decisions lead to a random distribution of the arrival aircraft, regardless of the schedule, and obviously affect the outcome of the arrival flow. This type of random arrival pattern leads to random spacing of the arrival aircraft as they approach a runway, which leads to wasted capacity.
Much of the current thinking concerning the airline/ATC delay problem is that it stems from the over scheduling by the airlines of too many aircraft into too few runways. While this may be true in part, it is also the case that the many apparently independent decisions that are made by an airline's staff and various ATC controllers may significantly contribute to airline/ATC delay/congestion problems.
These independent actions for each of the arriving flights, without regard to system effects, lead to a variance in the arrival flow, thus assuring a random outcome as the aircraft approach a destination airport. Mitigating the variance to reduce randomness and queuing represents a unique aspect of the present invention.
For illustrative purposes, one can compare the aircraft arrival flow into a busy airport to the actions of grade school children at the end of class. When the dismissal bell rings, if all of the students rush to the door, fighting to be the first one out, the throughput of the door is lowered. Conversely, if the students file out in an orderly and sequenced fashion, the actual throughput of the door is higher. In either case, the capacity of the door is the same, but by managing the flow through the door, the door's effective throughput is higher. The same can be said for an airport.
The explanation of the effects of randomness can be found in the mathematics of queue theory, which states that as the demand approaches capacity the queue waiting time increases at a rate proportional to the inverse of the difference between demand and capacity.
These delays are especially problematic since they are seen to be cumulative. FIG. 4 shows, for all airlines and a number of U.S. airports, the percentage of aircraft arriving on time during various one hour periods throughout a typical day. This on time arrival performance is seen to deteriorate throughout the day.
Where there are problems with over scheduling, the optimal, real-time sequencing of the various sizes of incoming aircraft could conceivably offer a possible mechanism for remedying such problems. For example, the consistent flow of aircraft at the runway end can increase effective capacity. Further, current aviation authority rules require different spacing between aircraft based on the size of the aircraft. Typical spacing between the arrivals of aircraft of the same size is three miles, or approximately one minute based on normal approach speeds. But if a small (Learjet, Cessna 172) or medium size aircraft (B737, MD80) is behind a large aircraft (B747, B767), this spacing distance is stretched out to five miles or one and a half to two minutes for safety considerations.
Thus, it can be seen that if a sequence of ten aircraft is such that a large aircraft alternates every other one with a small aircraft, the total distance of the arrival sequence of aircraft to the runway (5+3+5+3+5+3+5+3+5+3) is 40 miles. But if this sequence can be altered to put all of the small aircraft in positions 1 through 5, and all of the very large aircraft in slots 6 through 10, the total distance of the arrival sequence of aircraft to the runway is only 30 miles, since the spacing between the aircraft is consistently 3 miles. If the sequence is altered to the second scenario, the ten aircraft can land in a shorter period of time, thus freeing up additional landing slots behind this group of ten aircraft.
Unfortunately, to correct over capacity problems in the current art, the controller only has one option. They take the first over-capacity aircraft that arrives at the airport and move it backward in time. The second such aircraft is moved further back in time, the third, even further back, etc. Without a process in the current art to move aircraft forward in time or manage the arrival sequence in real time, the controller has only one option—delay the arrivals.
The current art of aircraft flow sequencing (to assure proper aircraft separation) to an airport can be broken down into seven distinct tools used by air traffic controllers, as applied in a first come, first serve basis, include:
1. Structured DogLeg Arrival Routes—The structured routings into an arrival fix are typically designed with doglegs. The design of the dogleg is two straight segments joined by an angle of less than 180 degrees. The purpose of the dogleg is to allow controllers to cut the corner as necessary to maintain the correct spacing between arrival aircraft.
2. Vectoring and Speed Control—If the actual spacing is more or less than the desired spacing, the controller can alter the speed of the aircraft to correct the spacing. Additionally, if the spacing is significantly smaller than desired, the controller can vector (turn) the aircraft off the route momentarily to increase the spacing. Given the last minute nature of these actions (within 100 mile of the airport), the outcome of such actions is limited.
3. The Approach Trombone—If too many aircraft arrive at a particular airport in a given period of time, the distance between the runway and base leg can be increased; see FIG. 5. This effectively lengthens the final approach and downwind legs allowing the controller to “store” or warehouse in-flight aircraft. A problem with this approach is that as the number of aircraft increases, the controller is required to handle more and more aircraft, such that his/her communication requirements also increase. The effect of such an increase is that while talking to one aircraft, the controller's instruction to another aircraft to turn towards the final approach is delayed slightly, which increases the spacing between aircraft on final approach and landing. Even a delay of ten seconds on such a call increases the spacing between such aircraft by approximately one mile. Three such delayed calls and a runway landing slot is missed. As was described above, the runway capacity remained unchanged, but its throughput was decreased.
4. Miles in Trail—If the approach trombone can't handle the over demand for the runway asset, the ATC system begins spreading out the arrival/departure flow linearly. It does this by implementing “miles-in-trail” restrictions. Effectively, as the aircraft approach the airport for landing, instead of 5 to 10 miles between aircraft on the linear arrival/departure path, the controllers begin spacing the aircraft at 20 or more miles in trail, one behind the other; see FIG. 6.
5. Ground Holds—If the separation authorities anticipate that the approach trombone and the miles-in-trail methods will not hold the aircraft overload, aircraft are held at their departure point and metered into the system using assigned takeoff times.
6. Holding—If events happen too quickly, the controllers are forced to use airborne holding. Although this can be done anywhere in the system, this is usually done at one of the arrival fixes to an airport. Aircraft enter the “holding stack” from the enroute airspace at the top; see FIG. 7. Each holding pattern is approximately 10 to 20 miles long and 3 to 5 miles wide. As aircraft exit the bottom of the stack towards the airport, aircraft orbiting above are moved down 1,000 feet to the next level.
7. Reroute—If a section of airspace, enroute center, or airport is projected to become overloaded, the aviation authority occasionally reroutes individual aircraft over a longer lateral route to delay the aircraft's entry to the predicted congestion.
CAA's current air traffic handling procedures are seen to result in significant inefficiencies. For example, pilots routinely mitigate some of the assigned ground hold or reroute orders by increasing the aircraft's speed during its flight, which often yields significantly increased fuel expenses. Also, vectoring and speed control by the ATC controller are usually accompanied with descents to a common altitude which may often be far below the aircraft's optimum cruise altitude, again with the use of considerable extra fuel. Further, the manual aspects of the sequencing and arrival ATC tasks can result in significantly greater separations between aircraft than are warranted; thereby significantly reducing an airport's landing capacity.
Thus, despite the above noted prior art, airlines/CAAs/airports continue to need safer and more efficient methods and systems to better manage the arrival/departure flow of a plurality of aircraft into and out of a system resource, like an airport, or a set of system resources, so as to yield increased aviation safety and airline/airport/airspace operating efficiency.
3. Objects and Advantages
There has been summarized above, rather broadly, the prior art that is related to the present invention in order that the context of the present invention may be better understood and appreciated. In this regard, it is instructive to also consider the objects and advantages of the present invention.
It is an object of the present invention to provide a method and system which allows an aviation system (e.g., an airline, airport or CAA) to better achieve its specified safety and operational efficiency goals with respect to the arrival and departure of a plurality of aircraft at a specified system resource, like an airport, or set of resources, thereby overcoming the limitations of the prior art described above.
It is another object of the present invention to present a method and system for the real time management of aircraft that takes into consideration a wider array of real time parameters and factors that heretofore were not considered. For example, such parameters and factors may include: aircraft related factors (i.e., speed, fuel, altitude, route, turbulence, winds, and weather) and ground services and common asset availability (i.e., runways, airspace, Air Traffic Control (ATC) services).
It is another object of the present invention to provide a method and system that will enable the airspace users to increase their safety and efficiency of operation.
It is yet another object of the present invention to provide a method and system that will allow an airport or other system resource to enhance its overall operating efficiency, even at the possible expense of its individual components that may become temporarily less effective. After the system's overall operation is optimized, then, as a secondary task, the present invention tries to enhance the efficiency of the individual components (i.e., meets a specific airline's business needs if provided) as long as they do not degrade the overall, optimized solution.
It is a further object of the present invention to provide a method and system that analyzes numerous real time information and other factors simultaneously, identifies system constraints and problems as early as possible, determines alternative possible trajectory sets, chooses the better of the evaluated asset trajectory sets, implements the new solution, and continuously monitors the outcome.
It is still a further object of the present invention to temporally manage the flow of aircraft into or out of a specific system resource in real time to prevent that resource from becoming overloaded. Further, if the outcome of prior events puts demand for that system resource above capacity, it is then the object of the present invention to maximize the throughput of the now constrained system resource with a consistent, more optimally sequenced flow of aircraft to/from that system resource.
It is an additional object of the present invention to minimize the large temporal variations to arrival/departure flows so as to mitigate the effects of randomness and queuing.
Such objects are different from the current art, which manages aircraft into or out of a specific resource linearly using distance based processes, or limits access to the entire system, not just the specific constrained system resource.
These and other objects and advantages of the present invention will become readily apparent as the invention is better understood by reference to the accompanying summary, drawings and the detailed description that follows.